Spondylisthesis reduction system

ABSTRACT

A system for reducing deformities of the vertebrae in the spine includes a first reduction assembly, a second reduction assembly, and a reduction drive assembly. The first reduction assembly is configured for attachment to a first reduction tower that attaches to a first vertebra. The second reduction assembly is configured for attachment to a second reduction tower that attaches to a second vertebra. The reduction drive assembly includes an arcuate rack gear operably coupling the first reduction assembly to the second reduction assembly to translate the first reduction assembly relative to the second reduction assembly along an arcuate path in a first plane.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/875,612, filed Jan. 19, 2018—now U.S. Pat. No. 10,820,932—which is adivisional of U.S. application Ser. No. 14/539,567, filed on Nov. 12,2014—now U.S. Pat. No. 10,172,656—which claims priority to U.S.Provisional Patent No. 61/902,993, filed Nov. 12, 2013. Each of theseapplications is incorporate herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure generally relates to the field of spinalorthopedics, and more particularly to instruments for reducingspondylolisthesis.

BACKGROUND

The spine is a flexible column formed of a plurality of bones calledvertebrae. The vertebrae are hollow and piled one upon the other,forming a strong hollow column for support of the cranium and trunk. Thehollow core of the spine houses and protects the nerves of the spinalcord. The different vertebrae are connected to one another by means ofarticular processes and intervertebral, fibrocartilaginous bodies.Various spinal disorders may cause the spine to become misaligned,curved, and/or twisted or result in fractured and/or compressedvertebrae. It is often necessary to surgically correct these spinaldisorders.

The spine includes seven cervical (neck) vertebrae, twelve thoracic(chest) vertebrae, five lumbar (lower back) vertebrae, and the fusedvertebrae in the sacrum and coccyx that help to form the hip region.While the shapes of individual vertebrae differ among these regions,each is essentially a short hollow shaft containing the bundle of nervesknown as the spinal cord. Individual nerves, such as those carryingmessages to the arms or legs, enter and exit the spinal cord throughgaps between vertebrae.

Spondylolisthesis is the anterior or posterior displacement of avertebra of the vertebral column in relation to the vertebra below. Inthe lower region of the back where the lumbar vertebrae meet the sacrum,spondylolisthesis may occur more frequently. For example, at the L5-S1level, the fifth lumbar vertebra may slip forward or in the anteriordirection relative to the first level of the sacrum. Treatment forspondylolisthesis depends on the severity of the slippage. For severecases, surgical correction is required.

Various systems and methods are known to alleviate and correctspondylolisthesis. For example, German Patent 41 27 303, filed Aug. 17,1991 (also disclosed in European Patent No. 0528177, filed Jul. 16,1992) to Aesculap A G, discloses such a device. Other devices includeU.S. Pat. No. 6,565,568, filed Sep. 28, 2000 to Rogozinski and U.S. Pat.Pub. No. 2009/0216237, filed Jun. 30, 2006 to Frezal et al. However,some of these systems may be difficult to maneuver, attach, and removefrom screw heads. Some of these systems may make it difficult to insertand secure fixation rods after correcting the slippage without removingportions of the systems.

The present invention seeks to overcome these problems, and others.

SUMMARY

Provided herein are systems, apparatuses, and methods for reducingdeformities in the spine.

A system for reducing deformities of the vertebrae in the spine includesa first reduction assembly, a second reduction assembly, and a reductiondrive assembly. The first reduction assembly is configured forattachment to a first reduction tower that attaches to a first vertebra.The second reduction assembly is configured for attachment to a secondreduction tower that attaches to a second vertebra. The reduction driveassembly includes an arcuate rack gear operably coupling the firstreduction assembly to the second reduction assembly to translate thefirst reduction assembly relative to the second reduction assembly alongan arcuate path in a first plane.

In other features, the first reduction assembly is operably coupled withthe arcuate rack gear to enable translation of the first reductionassembly relative to the arcuate rack gear along a linear path in asecond plane that is parallel to the first plane. In yet other features,the first reduction assembly is operably coupled with the arcuate rackgear to enable rotation relative of the first reduction assemblyrelative to the arcuate rack gear in a third plane that is perpendicularto the first plane. In still other features, the first reductionassembly is configured to rotatably couple with a proximal end of thefirst reduction tower to permit rotation relative to the first reductiontower in a fourth plane perpendicular to the second plane.

In other features, the second reduction assembly is configured torotatably couple with a proximal end of the second reduction tower topermit rotation relative to the second reduction tower in a fifth planeperpendicular to the first plane. In yet other features, the arcuaterack gear is pivotally coupled with a receiver that receives a loadtransfer link of the first reduction assembly.

In still other features, the reduction drive assembly comprises areduction lever coupled with a pinion gear configured to engage anddrive the arcuate rack gear. The reduction drive assembly includes areduction pawl to restrict movement of the arcuate rack gear to a singledirection. The reduction drive assembly includes a locking pawl to lockthe arcuate rack gear in place.

In yet other features, the reduction drive assembly is configured totranslate the arcuate rack gear along a curved path having a center ofrotation behind and below a distal end of the second tower assembly.

A system for reducing deformities in the spine includes a first towerassembly, a first reduction assembly, a second tower assembly, and asecond reduction assembly. The first reduction assembly is operablycoupled to a proximal end of the first tower assembly. The secondreduction assembly is operably coupled to a proximal end of the secondtower assembly. The second reduction assembly further includes areduction drive assembly. The reduction drive assembly includes a rackhaving an arcuate profile driven by a pinion gear. The reduction driveassembly is operably coupled to the first reduction assembly such thatthe reduction drive assembly transmits a leverage and causes relativemovement of the first tower assembly from the second tower assembly froman unreduced state into a reduce state.

In other features, the first reduction assembly further includes a loadtransfer link receiver and the second reduction assembly furthercomprises a load transfer link member. The load transfer link member andthe load transfer link receiver are operably engaged and freelytranslatable relative to one another. The load transfer link member isdisposed at an end of the arcuate rack.

In other features, a locking lever operably couples to the pinion gear.In yet other features, the first reduction assembly and the secondreduction assembly are operably coupled by a load transfer link member,at least a portion of the member having stepped features to define aratcheted portion, and a load transfer link receiver, at least a portionof the receiver being configured to engage the ratcheted portion of themember.

In still other features, the arcuate rack translates in a single planerelative to the second reduction assembly. In yet other features, thearcuate rack translates along a curved path having a center of rotationbehind and below a distal end of the second tower assembly.

In yet other features, the reduction drive assembly further includes areduction lever operably coupled to the pinion and the second reductionassembly further includes a handle member. In still other features, thereduction drive assembly further includes a reduction pawl operablycoupled to the reduction lever and the pinion and a locking pawloperably coupled to the rack.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying figures, like elements are identified by likereference numerals among the several preferred embodiments of thepresent invention.

FIG. 1A is a first isometric view of the system of the presentinvention; and FIG. 1B is a second isometric view of FIG. 1A.

FIG. 2A is a side view of a section of human spine, illustratingdisplacement of the L5 vertebra due to spondylolisthesis.

FIG. 2B is a first view of a portion of the spine and associated bonescrews for use with the system according to the principles of thepresent disclosure.

FIGS. 3A-3D are cross-sectional views of a tower assembly of the systemand one of the bone screws according to the principles of the presentdisclosure.

FIG. 3E is an illustration of an exemplary polyaxial screw, towerassembly, and screw driver for use with the present invention.

FIGS. 4A-4B illustrate the process of preparing the vertebrae fortreatment, by installing the polyaxial screws and towers by use of thedriver.

FIG. 5 is a perspective view of one embodiment of a first reductionassembly of the present invention.

FIG. 6A is an isometric view of one embodiment of a second reductionassembly of the present invention; and FIG. 6B is a cross-sectional viewof FIG. 6A.

FIGS. 7A-7B illustrate the process of coupling the first reductionassembly to the first tower.

FIGS. 8A-8C illustrate the process of coupling the second reductionassembly to the second tower, and engaging the second reduction assemblywith the first reduction assembly.

FIGS. 9A-9B illustrate the process of provisionally locking thepolyaxial screws with provisional lockers, prior to reduction.

FIG. 10A is an isometric view of a driver being applied to a reductiondriver assembly of the second reduction assembly; and FIG. 10B is a sideview of FIG. 10A.

FIG. 11A is an isometric view of the installed system of the presentinvention, after reduction; and FIG. 11B is a side view of FIG. 11A.

FIG. 12 is a side view of the installed system of the present invention,after reduction and distraction of the vertebrae.

FIGS. 13A-13B show exemplary datum curves for the path of movement andcenters of rotation of the system of the present invention.

FIGS. 14A-14B show an exemplary curvature of the system of the presentinvention before reduction in retracted and extended states.

FIGS. 15A-15B show an exemplary state of the system of the presentinvention after reduction in extended and retracted states.

FIGS. 16A-16D show an alternative embodiment of the present invention,including a reduction lever in place of the knob.

FIGS. 17A-17B show an alternative embodiment of the device of FIGS.16A-16D, including a reduction handle member.

FIG. 18 illustrates the stages of reduction using the alternativeembodiment of FIGS. 16A-16D.

FIGS. 19A and 19B illustrate perspective views of an exemplary systemfor reduction of a spinal deformity coupled with first and secondreduction towers.

FIG. 20 is a perspective view of a first reduction assembly.

FIG. 21 is a perspective view of a second reduction assembly.

FIG. 22 is a perspective view of an arcuate rack gear with a pivotallycoupled receiver.

FIGS. 23A-23C, 24A-24C, and 25A-25C illustrate the reduction assembly ofFIGS. 19A and 19B in various stages of reduction.

FIG. 26 is an exploded view of the second reduction assembly of FIG. 21.

FIG. 27 is an exploded view of the arcuate rack gear and receiver ofFIG. 22 .

FIG. 28 is an exploded view of the first reduction assembly of FIG. 20 .

FIG. 29 is an exploded view of an exemplary reduction tower.

FIG. 30 is a perspective view of a pair of systems as shown in FIGS. 19Aand 19B including right and left portions that are mirror images.

DETAILED DESCRIPTION

The foregoing and other features and advantages of the invention areapparent from the following detailed description of exemplaryembodiments, read in conjunction with the accompanying drawings. Thedetailed description and drawings are merely illustrative of theinvention rather than limiting, the scope of the invention being definedby the appended claims and equivalents thereof.

Embodiments of the invention will now be described with reference to theFigures, wherein like numerals reflect like elements throughout. Theterminology used in the description presented herein is not intended tobe interpreted in any limited or restrictive way, simply because it isbeing utilized in conjunction with detailed description of certainspecific embodiments of the invention. Furthermore, embodiments of theinvention may include several novel features, no single one of which issolely responsible for its desirable attributes or which is essential topracticing the invention described herein. The words proximal and distalare applied herein to denote specific ends of components of theinstruments described herein. A proximal end refers to the end of aninstrument nearer to an operator of the instrument when the instrumentis being used. A distal end refers to the end of a component furtherfrom the operator and extending towards the surgical area of a patientand/or the implant.

Reference to the invention may also be described with respect tocoronal, sagittal, and transverse axes of the body. The coronal axisrefers to an axis running substantially from front (anterior) to back(posterior) of the body and extending through the mid-section. Thesagittal axis refers to an axis running substantially from left to rightof the body and extending through the mid-section to intersect thecoronal axis at a right angle. The transverse axis refers to an axisrunning substantially from head to toe of the body and crossing thepoint where the coronal and sagittal axes intersect at a right angle.Furthermore, the coronal, sagittal, and transverse planes refer to thestandard definitions associated with each term. Namely, the coronalplane being a plane perpendicular to the coronal axis and formed by thetransverse and sagittal axes, the sagittal plane being perpendicular tothe sagittal axis and formed by the coronal and transverse axes, and thetransverse plane being perpendicular to the transverse axis and formedby the sagittal and coronal axes.

For a mid to high grade spondylolisthesis at the L5-S1 level, theanatomy is exposed and bone screws are placed in the pedicles of the L5lumbar vertebra bilaterally near the cephalad end of the sacrum. Bonescrews are also placed in the sacrum. A system of instruments may beused to reposition the L5 vertebra relative to the S1 level. The systemmay comprise a set of mirrored tower assemblies which attach to the topsof the screw heads.

Generally speaking, the sacral (second) towers may provide a relativeground reference for the reduction apparatus while the lumbar (first)towers may act as load transfer structures. A drive apparatus mounted tothe sacral towers provides forced to produce the necessary anatomicalcorrection. The tower assemblies transmit the leverage generated by thedrive apparatus into a posterior load on the L5 vertebral body. Thesystem applies a generally posteriorly directed force to the vertebralbody while allowing the vertebral body to travel posteriorly along apath of least resistance. The system may or may not dictate an exactpath the vertebral body takes during the reduction procedure. Rods canthen be placed in the heads of the bone screws and secured in placewithout removing the system.

Benefits of the present invention include the ability to attach thetower assemblies and remove them from the screw head in a single action.The present invention may also provide the ability to insert fixationrods and secure them with set screws without removing the towers.

Referring to FIGS. 1-15 , a system 100 for correcting spondylolisthesisis disclosed. The system 100 is shown in conjunction with two sets ofbone screws inserted into two vertebrae of a spinal column in FIGS. 4A-Band 7-12. As shown in FIGS. 1A and 1B, the system 100 may include firsttower assembly 102 and second tower assembly 104. The tower assemblies102 and 104 may be attached to bone screws at the distal end of thetower assemblies 102 and 104. For example, in FIGS. 2A and 2B, a firstset of bone screws 10 has been inserted into a fifth lumbar vertebra L5and a second set of bone screws 12 has been inserted into the firstlevel of the sacrum S1 through a minimally invasive surgery (MIS)technique, or through any other technique as known in the art. Thesystem 100 may be used in conjunction with a spinal fixation system thatincludes one or more fixation rods (not shown) disposed through a lumenof the tower assemblies 102 and 104 and setscrews (not shown) topermanently align and rigidly fix two or more levels of the spinalcolumn such as the L5 and S1 levels. Exemplary bone screws and fixationsystems may be found in U.S. Pub. No. 2010/0036443 and U.S. Pub. No.2009/0171391 both of which are incorporated herein by reference in theirentirety. Bone screws 10, 12 may comprise polyaxial type screws,monoaxial type screws, or fixed screws, as known in the art.

Although the system 100 of the present disclosure is described hereinwith reference to the L5 and S1 levels, the system 100 may be used inother regions of the spine where spondylolisthesis or other slippage ofvertebral bodies may occur. As shown in FIGS. 1A-B the tower assemblies102 and 104 may removably couple with sets of bones screws 10 and 12respectively via MIS procedures, or other procedures as known in theart. The tower assemblies 102 and 104 include a mating feature 109 onthe proximal end of the tower assemblies 102 and 104 to couple thetowers 102 and 104 to the reduction assemblies 200 and 300 and transmita leverage generated by the reduction assemblies 200 and 300 to causerelative movement of the tower assembly 102 from tower assembly 104. Thefirst tower assembly 102 may be referred to as a lumbar tower assembly.The second tower assembly 104 may be referred to as a sacral towerassembly. The tower assemblies 102 and 104 may couple to the bone screws10 and 12 respectively and in substantially similar fashion.

Anatomy and the degree of severity of the spondylolisthesis will varyfrom patient to patient. Thus, after placement of the bone screws 10,12, longitudinal axes of the bone screws 10, 12 may not be co-planerwhen observed from a viewpoint normal to the transverse plane as shownby FIG. 2A. For example, an angle A may be formed by the axes.Additionally, an angle between the longitudinal axes may vary whenobserved from a viewpoint normal to the sagittal plane as shown by FIG.2B. For example, an angle B may be formed by the axes. To accommodatefor the variations between patients and severity of thespondylolisthesis, various interconnecting elements of the system 100provide sufficient degrees of freedom to allow for variations inplacement and actuation of the system 100. Each tower assembly 102 and104 may include additional features that enable positioning andalignment of the L5 vertebra relative to the S1 level of the sacrumprior to fixation with the rods. Because each set of tower assembliesincludes mirrored components, references throughout this description mayrefer to left sides and right sides of the system 100 interchangeably.Left and right may indicate the left side and right side from theviewpoint of a patient. Furthermore, each left and right tower assembly102 and 104 may couple with the bone screws in substantially similarfashion.

As shown in FIGS. 3A-D, a portion of one tower assembly is shown inconjunction with one of the bone screws. For ease of discussion, thedescription herein will refer to one of the lumbar tower assemblies 102and one of the L5 vertebra bone screws 10. The lumbar tower assembly 102may include features to enable single-action coupling with and removalfrom a receiving portion 20 of the bone screw 10 (receiving portion 24for bone screw 12). For example, the lumbar tower assembly 102 mayinclude clips 106 in sidewalls 108 of the tower assembly 102. The clips106 may extend along the length of the sidewall and may pivot on pins110. Each clip 106 may include a proximal end with grips or pads 112which may be depressed by the surgeon to actuate the clip 106. Each clip106 may include a distal end with a projection 114, such as a boss orprotrusion that extends radially inward from the clip 106. Theprojection 114 may engage with a recessed portion 22, such as a bore,pocket, or indentation, of the receiver portion 20 of the bone screw 10.A bias mechanism 116, such as a coil spring, leaf spring, or otherelastic mechanism, may position the clip 106 into an engaged or closedposition with the receiver portion 20. The surgeon may apply force viathe pads 112 to position the clip 106 into a disengaged or openposition, wherein the projection 114 disengages the receiver portion 20,thus permitting removal of the tower assembly 102 from the screw 10. Theprojection 114 may include a ramped surface 118 or taper to facilitatecoupling with the receiver portion 20 without actuating the clips 106 tothe open position. The proximal end of the tower assemblies 102 and 104may also include a mating feature 109 as to allow the reduction assemblymembers 200 and 300 to be operably coupled to the proximal ends of thetower assemblies 102 and 104. The mating feature 109 may protrude intothe surface of the sidewalls 108 and may also protrude outwards from thesurface of the sidewalls 108, as to provide a lipped and indented matingfeature 109 with a space therebetween.

In some embodiments, as shown in FIGS. 1A-B, 3E, 4A-B, and 7-12, thetowers 102, 104 may further comprise quick-release engagement features150, 152. In one embodiment, quick-release engagement features 150, 152may comprise an aperture through a proximal portion of the wall 108 ofthe towers 102, 104. The quick-release engagement features 150, 152 mayoperably engage with a quick-release trigger 212 on the first reductionassembly 200 or a quick-release trigger 312 on the second reductionassembly 300. In some embodiments, the quick-release engagement features150, 152 and triggers 212, 312 prevent rotation the first and secondreduction assemblies 200, 300 relative to the towers 102, 104.

FIG. 3E illustrates one embodiment of an exemplary pedicle screw 10 andtower 102. The tower 102 may further comprise a quick-release engagementfeature 150 (or quick-release engagement feature 152 for tower 104). Inone embodiment, quick-release engagement feature 150 may comprise anaperture through a proximal portion of the wall 108 of the tower 102. Adriver 80 may be used to install the pedicle screws 10, 12 in the spine.The driver 80 may be any suitable pedicle screw driver, as known in theart. In one embodiment, the driver 80 may be configured for MIS typescrew insertion.

FIG. 4A illustrates an exemplary embodiment of the pedicle screws 10, 12and towers 102, 104 being inserted into the chosen vertebrae. In FIG.4A, pedicle screw 12 and tower 104 have already been installed, and thedriver 80 is inserted within the tower 102 in order to install pediclescrew 10 and tower 102, using an MIS type technique. FIG. 4B shows bothpedicle screws 10 and 12 installed in their respective vertebrae, withthe driver 80 removed.

Continuing now with FIG. 5 , the first reduction assembly 200 is shown.The first reduction assembly 200 and tower 102 may include additionalfeatures that link to the second reduction assembly 300 and tower 104.Once linked, the second reduction assembly 300 may be used to applyforces on the first reduction assembly 200 to reposition the L5vertebra. For example, the first reduction assembly 200 may include aload transfer ring 206, a body member 210, and a load transfer linkmember/rod 230. The transfer ring 206 may be coupled to the proximal endof the lumbar tower 102, such as by mating features 109 and/orquick-release engagement feature 150 and quick-release trigger 212. Inone embodiment, the transfer ring 206 may rotate about a longitudinalaxis of the lumbar tower 102. In one embodiment, the transfer ring 206is fixedly coupled to the proximal end of the lumbar tower 102.

In one embodiment, the first reduction assembly 200 may further comprisea quick-release mechanism. A quick-release trigger 212 may be operablycoupled to the load transfer ring 206 as to lock the proximal end of thetower assembly 102 in place. The quick-release trigger 212 may berotatably coupled to the load transfer ring 206 of the first reductionassembly 200 by way of an opening, a pin, a spring, and/or similar meansas known in the art. The quick-release trigger 212 may include a lockingfeature as to mate with the quick-release feature 150 on the proximalend of the first tower assemblies 102. The quick release trigger 212 andthe load transfer ring 206 may secure the first reduction assembly 200to the first tower assembly 102. The transfer link member/rod 230 may befixedly coupled to a portion of the body member 210 of the firstreduction assembly 200, and extend outward therefrom.

In an alternative embodiment (not shown), the first reduction assembly200 may comprise load transfer link receiver (as discussed below inrelation to the second reduction assembly 300) rather than the loadtransfer link member/rod 230.

The transfer link member/rod 230 extends away from the body member 210,a first end of the transfer link member/rod 230 disposed at the bodymember 210. A second end of the transfer link member/rod 230 may beconfigured to engage with the load transfer link receiver 360 of thesecond reduction assembly 300.

In an alternative embodiment, the transfer link member/rod 230 mayfurther comprise means for distraction. In one embodiment, the means fordistraction may comprise a ratcheted portion of the link member/rod 230,such that the link member/rod 230 includes stepped features as to matewith distraction features on the second reduction assembly 300. In oneembodiment, the load transfer link receiver 360 may further comprise adistraction slide lock, distraction trigger, and distraction lockingtube configured to operably engage with the link member/rod 230. Suchdistraction means is more fully discussed in commonly owned andco-pending application Ser. No. 13/835,938, incorporated herein byreference in its entirety. Similar means for distraction, as known inthe art, may also be used.

Referring to FIGS. 6A-B, the second reduction assembly 300 may include aload transfer ring 306 for mounting the second reduction assembly 300 onthe proximal end of the second tower assembly 104. A quick-releasetrigger 312 may be operably coupled with the load transfer ring 306 asto lock the second reduction assembly 300 to the proximal end of thetower assembly 104. The quick-release trigger 312 may be rotatablycoupled to the load transfer ring 306 of the second reduction assembly300 by way of an opening, a pin, a spring, and/or similar means as knownin the art. The quick-release trigger 312 may include a locking featureas to mate with the quick-release feature 152 on the proximal end of thesecond tower assemblies 104. The quick-release trigger 312 and the loadtransfer ring 306 may secure the second reduction assembly 300 to thesecond tower assembly 104. The second reduction assembly 300 may furthercomprise a reduction drive assembly 350. The reduction drive assembly300 may be a rack and pinion type drive. In one embodiment, thereduction drive assembly 350 may comprise a body member 310, an arcuateor curved rack 352, a pinion 354 fixedly coupled to a knob 356, and alocking lever 358. The rack 352, pinion 354 and knob 356, and lockinglever 358 are all operably and movably coupled to the body member 310.The rack 352 and body member 310 are configured such that the rack 352may only translate in a single plane relative to the body member 310.The rack 352 may comprise any suitable arc or curvature to permitreduction in the vertical and horizontal directions simultaneously. Thepinion 354 and knob 356 may be rotatably coupled to the body member 310,such as through one or more apertures in the body member 310.

In one embodiment, the pinion 354 includes a bore through which a shaftis disposed, the shaft being fixed to the knob 356. The bore and shaftmay be configured to engage such that rotation of the knob 356 androtation of the pinion 354 are coupled. The pinion 354 may comprise around gear having a plurality of teeth configured to engage with aplurality of teeth 351 on the rack 352 such that rotational motion ofthe pinion 354 causes linear motion of the rack 352. In someembodiments, the pinion may comprise an alternative shape, so long asthe pinion 354 is configured to engage the rack 352 and convertrotational force on the pinion 354 into lateral translation of the rack352, as known in the art. The teeth of the rack 352 and pinion 354 maycomprise any suitable configuration such that the translation of therack 352 is controlled. The locking lever 358 may be operably coupled tothe body member 310 and the pinion 354. In one embodiment, the lockinglever 358 has a locking state and a released state, where the lockingstate is the default state of the locking lever 358. To release thelocking lever 358, the lever 358 may be actuated so as to disengage thelever 358 from the pinion 354. In one embodiment, the locking lever 358permits one-way rotation of the pinion 354, and must be released priorto reverse motion of the pinion 354. The reduction drive assembly 350further comprises a load transfer link receiver 360. The receiver 360may be fixedly coupled to the rack 352. As the rack 352 is advanced byrotation of the pinion 354, the receiver 360 is translated along thesame arc as the rack 352.

In an alternative embodiment (not shown), the second reduction assembly300 may comprise a load transfer link member/rod (as discussed abovewith regard to the first reduction assembly 200) rather than thereceiver 360.

In an alternative embodiment, the load transfer link receiver 360 mayfurther comprise means for distraction. In one embodiment, the means fordistraction may comprise a distraction slide lock, a distractiontrigger, and a locking tube. In one embodiment, the load transferlink/rod 230 may further comprise a ratcheted portion including steppedfeatures as to mate with the distraction slide lock, trigger, and tube.Such distraction means is more fully discussed in commonly owned andco-pending application Ser. No. 13/835,938, incorporated herein byreference in its entirety. Similar means for distraction, as known inthe art, may also be used.

FIGS. 14A-B show the system 100 in an unreduced state where the loadtransfer link member/rod 230 can move freely during the reductionrelative to the load transfer link receiver 360. The L5 vertebrae may bereduced into position by levering off of the placed screw 12 in the S1vertebrae, and the reduced state of the system 100 is shown in FIGS.15A-B. Distraction can be applied before (see FIG. 14B) or after (seeFIG. 15A) reduction of the L5. In some embodiments, the system 100 mayinclude features to hold the distraction in place before, during, orafter reduction. In one embodiment, a distractor may be incorporatedinto the system 100, as discussed above. In another embodiment, a screwto screw distractor may be used to provide the distraction. In anotherembodiment, any means for distraction, as known in the art, may be usedto provide the distraction, and/or incorporated into the system 100.

In one embodiment, the load transfer link member/rod 230 is freelymovable relative to the load transfer link receiver 360. As such, theload transfer link member/rod 230 may be in an extended state (see FIGS.14B and 15A) or a retracted state (see FIGS. 14A and 15B).Alternatively, the load transfer link member/rod 230 may be in apartially extended state between the extended state and the retractedstate. Extension of the load transfer link member/rod 230 may allow thesystem 100 to accommodate different spacings depending on the positionof the screws, vertebrae, etc. During reduction, the system 100 may relyon the surrounding tissues to hold the extended load transfer linkmember/rod 230 in position. The load transfer link member/rod 230 may beconfigured to have any length suitable for the particular procedure inwhich the system 100 is used.

FIGS. 7-12 illustrate the process of attaching and operating the system100.

FIGS. 7A-B illustrate the process of coupling the first reductionassembly 200 to the first tower 102. In FIG. 7A, the first reductionassembly 200 is being placed onto the proximal end of the first tower102, in the manner described above. FIG. 7B shows the first reductionassembly 200 after being coupled to the first tower 102.

FIGS. 8A-C illustrate the process of coupling the second reductionassembly 300 to the second tower 104, and engaging the second reductionassembly 300 with the first reduction assembly 200. In FIG. 8A, thesecond reduction assembly 300 is being placed onto the proximal end ofthe second tower 104, in the manner described above. FIG. 8B shows thesecond reduction assembly 300 after being coupled to the second tower104, and the load transfer link member/rod 230 engaging with the loadtransfer link receiver 360. FIG. 8C shows a side view of the embodimentof FIG. 8B, to highlight the displacement of the vertebrae.

FIGS. 9A-B illustrate the process of provisionally locking the polyaxialscrews with provisional lockers, prior to reduction. Prior to reduction,the pedicle screws 10, 12 may be provisionally locked to preventslippage of the screw heads during reduction. Provisional lockers 90,each having distal engagement tip 91 and proximal head 92, may be usedto provisionally lock the pedicle screws 10, 12. The lockers 90 may bedisposed within the towers 102, 104 such that the engagement tips 91engage the heads of the screws 10, 12. Once the tips 91 engage the headsof the screws 10, 12, the locker 90 may be rotated to provisionally lockthe screw heads. In one embodiment, shown in FIG. 9B, a driver 94 may beused to rotate the lockers 90. The driver 94 may be configured so as toincrease the torque that may be applied to rotate the lockers 90. Thedriver 94 may have a distal engagement member 96 that is configured toengage the heads 92 of the lockers 90. Once the screws 10, 12 areprovisionally locked, reduction may begin.

To drive the reduction, the knob 356 may be rotated to translate thearcuate rack 352 by rotation of the pinion 354. As shown in FIGS. 10A-B,in one embodiment, the driver 94 discussed above may be used to provideincreased torque on the knob 356 to drive the reduction. In oneembodiment, the knob 356 is configured to couple with the engagementmember 96 of the driver 94, such that rotation of the driver 94 rotatesthe knob 356.

As the knob 356 is rotated, the rack 352 is drawn back, or “cammed.”Exemplary depictions of the path of the rack 352 and screw 10 duringreduction are shown in FIGS. 13-15 .

FIGS. 11A-B show two views of the system 100 after reduction iscompleted, showing how the displaced vertebra is relocated by thereduction, as discussed above.

FIG. 12 is a side view of the installed system 100 of the presentinvention, after reduction and distraction of the vertebrae, asdiscussed above.

In one embodiment, the system 100 may be used to correctspondylolisthesis at the L5-S1 level of the spine. For example, in FIGS.2 a -b, 4 a-b, and 7-10, the L5 vertebra has slipped forward oranteriorly from the S1 level of the sacrum. The slippage may occur dueto degeneration of disc material between the L5 and S1 levels. Theslippage may occur from a fracture of degeneration of the vertebral bodyand/or from fracturing of the L5 vertebra. In some cases, bone growthmay occur on an upper surface of the S1 level due to rubbing from the L5vertebra. The system 100 may be used to reposition the L5 vertebra intoproper alignment with the S1 level and hold the L5 and S1 levels inplace while permanent fixation is added in the form of fixation rods andset screws.

The load transfer link member/rod 230 slidably engages with the transferload link receiver 360 to permit free translational movement of the L5vertebra in the sagittal plane. Movement of the L5 vertebra isaccommodated by the arcuate translation of the rack 352 and the tower102 and screw 10. As shown in FIGS. 11A-B, the knob 356 may be rotatedand the rack 352 translated Pass L5 level is brought into properalignment with the S1 level. As the L5 level is positioned posteriorly,the sliding engagement of the load transfer link member/rod 230 with thetransfer link receiver 360 allows the L5 vertebra to follow a path ofleast resistance. Once the vertebra L5 is properly aligned with the S1level of the sacrum, rods (not shown) may be inserted into the receivingportions 20, 24 of the screws 10 and 12, as known in the art. Each towerassembly 102 and 104 may also be cannulated to permit insertion ofsetscrews within the receiving portions 20, 24 of the screws 10 and 12to permanently secure the L5-S11 level. Additionally, a spacer or otherinterbody device may be secured between the L5 vertebra and S1 level ofthe sacrum. Bone material may be inserted with the spacer or interbodydevice to promote bone fusion and bone growth to permanently fuse theL5-S1 level.

In some embodiments, a distractor or distraction means may be appliedafter reduction is complete. The distractor or distraction means (notshown) may be used to increase the separation between the vertebrae asnecessary for any further procedures or steps, as shown in FIG. 12 .

FIGS. 13-15 show exemplary datum curves of the system 100 for the pathof movement and centers of rotation. As shown, the center of rotation1310 may be located behind and below the screw 12 of the second tower104. In some embodiments, the center of rotation 1310 substantiallycenters on the dome of the sacrum so that the natural curve of thesacrum may be followed and cammed around. The path of the screw 10during reduction is shown by curve 1320, which is the path the L5 screw10 will follow during reduction (see 13 a-b).

FIGS. 14A-B show exemplary datum curves of the system 100 beforereduction in retracted (FIG. 14A) and extended (FIG. 14B) states. FIGS.15A-B show exemplary datum curves of the system 100 after reduction inextended (FIG. 15A) and retracted (FIG. 15B) states.

An alternative embodiment of the device is shown in FIGS. 16A-D, wherethe device 600 may comprise a drive assembly 450 that uses a reductionlever 456 in place of the knob 356 to drive the pinion 454. In thisembodiment, the second reduction assembly 400 is generally similar tothe second reduction assembly 300. The reduction assembly 400 mayinclude a load transfer ring 406 for mounting the second reductionassembly 400 on the proximal end of the second tower assembly 104.

A quick-release trigger 412 may be operably coupled with the loadtransfer ring 406 as to lock the second reduction assembly 400 to theproximal end of the tower assembly 104. The quick-release trigger 412may be rotatably coupled to the load transfer ring 406 of the secondreduction assembly 400 by way of an opening, a pin, a spring, and/orsimilar means as known in the art. The quick-release trigger 412 mayinclude a locking feature as to mate with the quick-release feature 152on the proximal end of the second tower assemblies 104. Thequick-release trigger 412 and the load transfer ring 406 may secure thesecond reduction assembly 400 to the second tower assembly 104.

The second reduction assembly 400 may further comprise a reduction driveassembly 450. The reduction drive assembly 400 may be a rack and piniontype drive. In one embodiment, the reduction drive assembly 450 maycomprise a body member 410, an arcuate or curved rack 452, a pinion 454coupled to a reduction lever 456, and a locking pawl 458. The rack 452,pinion 454 and lever 456, and locking pawl 458 are all operably andmovably coupled to the body member 410. The rack 452 and body member 410are configured such that the rack 452 may only translate in a singleplane relative to the body member 410. The rack 452 may comprise anysuitable arc or curvature to permit reduction in the vertical andhorizontal directions simultaneously. The pinion 454 and reduction lever456 may be rotatably coupled to the body member 410, such as through oneor more apertures in the body member 410.

In one embodiment, the pinion 454 includes a bore through which a shaftis disposed, the shaft being fixed to the lever 456. The bore and shaftmay be configured to engage such that movement of the lever 456 androtation of the pinion 454 are coupled. The pinion 454 may comprise around gear having a plurality of teeth configured to engage with aplurality of teeth on the rack 452 such that rotational motion of thepinion 454 causes linear motion of the rack 452. In some embodiments,the pinion 454 may comprise an alternative shape, so long as the pinion454 is configured to engage the rack 452 and convert rotational force onthe pinion 454 into lateral translation of the rack 452, as known in theart. The teeth of the rack 452 and pinion 454 may comprise any suitableconfiguration such that the translation of the rack 452 is controlled.

In some embodiments, the reduction lever 456 may further comprise areduction pawl 470. The reduction pawl 470 may be configured to operablycouple the reduction lever 456 and pinion 454 such that actuation of thelever 456 moves the pinion 454 in a single direction. A locking ridge471 may be disposed on the reduction pawl 470, such that the lockingridge 471 is configured to engage the pinion 454 and permit one-waytranslation of the lever 456 relative to the pinion 454. In use, theridge 471 will freely permit the lever 456 to actuate in one directionto “load” the lever 456. As the lever 456 is actuated in the oppositedirection, the ridge 471 will engage the pinion 454 and cause the pinion4 to rotate with the lever 456, advancing the rack 452. A spring 472 maybe used to provide tension on the reduction pawl 470.

The locking pawl 458 may be operably coupled to the body member 410 andthe rack 452. In one embodiment, the locking pawl 458 has a lockingstate and a released state, where the locking state is the default stateof the locking pawl 458. To release the locking pawl 458, the pawl 458may be actuated so as to disengage the pawl 458 from the rack 452. Inone embodiment, the locking pawl 458 permits one-way translation of therack 452, and must be released prior to reverse motion of the rack 452.A locking ridge 459 may be disposed on the locking pawl 458, such thatthe ridge 459 is configured to engage the rack 452. The ridge 459 may beconfigured such that the rack 452 may advance in a single directionwithout release of the pawl 458. A torsion spring 476 may be operablycoupled to the pawl 458 and the body 410.

Together, the reduction pawl 470 and locking pawl 458 operate to permita ratchet-like functionality to the reduction drive assembly 450. One ofthe reduction pawl 470 and locking pawl 458 is engaged with either thepinion 454 or rack 452 in each direction of motion. As the lever 456 isbeing “loaded,” the locking pawl 458 engages the rack 452 to preventslippage of the reduction drive assembly 450, while the reduction pawl470 permits the lever 456 to freely rotate relative to the pinion 454.As the lever 456 is actuated to impart reduction, the locking pawl 458permits the rack 452 to freely translate relative to the locking pawl458, while the reduction pawl 470 engages the pinion 454 and causes thepinion 454 to rotate as the lever 456 is actuated. In this manner, thereduction drive assembly 450 may easily be operated through a pluralityof stages of partial reduction, as illustrated in FIG. 18 .

The reduction drive assembly 450 further comprises a load transfer linkreceiver 460. The receiver 460 may be fixedly coupled to the rack 452.As the rack 452 is advanced by rotation of the pinion 454, the receiver460 is translated along the same arc as the rack 452.

In an alternative embodiment (not shown), the second reduction assembly400 may comprise a load transfer link member/rod (as discussed abovewith regard to the first reduction assembly 200) rather than thereceiver 460.

FIGS. 17A-B show an alternative embodiment of the device illustrated inFIGS. 16A-D. The device 700 is generally identical to the device 600 ofFIGS. 16A-D, but the reduction drive assembly 450 may further comprise areduction handle member 480. The reduction handle member 480 provides agrip point to assist in actuation of the reduction lever 456. In oneembodiment, the reduction handle member 480 may comprise a generallyrectangular projection from the body member 410 of the reduction driveassembly 450. In some embodiments, the reduction handle member 480 maycomprise an alternative shape, as known in the art, including but notlimited to: a curved handle, a handle with finger grips, cylindrical,and/or the like.

Referring now to FIG. 19A through FIG. 29 , an assembly 800 forreduction of a spinal deformity includes similar features as thepreviously described embodiments. Like numerals are used for likefeatures throughout. The exemplary assembly 800 depicted may be usedalone or as a pair of assemblies including assembly 800 and a mirrorimage of assembly 800 as shown in FIG. 30 . For ease of discussion,assembly 800 is described below with reference to attachment to thespine on a left side of the vertebrae. The assembly 800 includesfeatures for attachment to tower assemblies 102 and 104 which may bereferred to as a cephalad tower assembly 102 and a caudal tower assembly104 described in greater detail with reference to FIG. 29 .

The assembly 800 includes first body member 210 and second body member410 which may include the same or similar load transfer rings 206 and406 respectively for attachment to the tower assemblies 102 and 104. Theassembly includes the load transfer link 230 extending from the firstbody member 210 to the receiver 460 of the rack 452. The rack 452 mayposition the cephalad tower assembly 102 relative to the caudal towerassembly 104 simultaneously in multiple planes and directions. A drivesystem 850 similar to the drive system 450 described above may couplewith the rack 452. The drive system 850 includes a similar drivemechanism for ratcheted engagement of the rack 452 via lever 456 whichselectively engages and disengages the rack 452 to advance and lock therack 452 in position. The reduction handle 480 may be used to apply aforce to the lever 456 to advance the rack 452. The receiver 460 may bepivotably coupled to a distal end of the rack 452 to permit additionalfreedom of movement of the attached cephalad tower assembly 102. Forexample, as shown in FIG. 22 , the rack 452 may be pivotably coupledwith the receiver 460 by a pin 461.

Referring now to figure sets including FIGS. 23A-23C, 24A-24C, and25A-25C, actuation of the assembly 800 demonstrates the multiple degreesor rotation and translation available for reducing a spinal deformity.The rack 452 may be advanced along an arcuate path AA in a first plane.The load transfer link 230 may slidably advance along a linear path BBwithin the receiver 460. The linear path BB may lie in the first planeor a parallel plane and along a common longitudinal axis shared by abore in the receiver 460 and the load transfer link 230. The receiver460 may rotate in a path CC about a distal end of the rack 452. The pathCC may lie in the first plane or a parallel plane. The body member 210may rotate in a circular path DD in a second plane normal to thelongitudinal axis and substantially perpendicular to the first plane.For example, the body member 210 may be rotatable coupled to an end ofthe load transfer link 230. Alternately, the body member 210 may befixed to the end of the load transfer link but may rotate freely withinthe receiver 460 for the same effect. Last, the cephalad tower assembly102 (not shown) may rotate within the load transfer ring 206 in acircular path EE in a third plane that is substantially perpendicular tothe second plane and the first plane.

FIG. 26 illustrates an exploded view of the body member 410 and drivemechanism 450 of the assembly 800. FIG. 27 illustrates an exploded viewof the rack 456 and receiver 460. FIG. 28 illustrates an exploded viewof the body member 210 and load transfer link 230. FIG. 29 illustratesan exploded view of a tower assembly 102/104.

Referring now to FIG. 26 , the reduction handle 480 may be offset fromthe load transfer ring 406 and extend parallel to a longitudinal axis ofthe load transfer ring 406. The reduction lever 456 may be pivotallycoupled to the handle 480 by a pinion pin 455. The pinion pin maycapture the pinion gear 454 within a portion of the reduction lever 456.Actuation of the reduction lever 456 thus turns the pinion gear 454which in turn translates the rack 452. The locking pawl 458 may also bepivotally coupled to the reduction handle 480 by a guide pin 413. Thelocking pawl 458 may be biased into engagement with the rack 452 to lockthe rack 452 in a predetermined position after advancement by thereduction lever 456. The reduction pawl 470 may be biased via spring 472and allow movement of the rack 452 in a single direction as describedabove.

Referring now to FIG. 27 , the rack 452 pivotally couples with thereceiver 460 by engagement of a pivot pin 461 with bores 462 in an endof the receiver 460 and a bore 463 in an end of the rack 452. The rack452 may further include a plurality of teeth 451 on a proximal surfacefor engagement with the pinion gear 454 and guide channels 453 on sidesthat engage portions of the body member 410 to guide the arcuatetranslation of the rack 452. In FIG. 28 , the body member 210 maypivotally couple with the load transfer link 230 via a bore 211 in oneend of the body member 210. The bore 211 may extend perpendicular to theload transfer ring 206.

FIG. 29 illustrates an exemplary tower such as the first or cephaladtower 102. The tower 102 may include all or some of the features asdescribed above with reference to FIGS. 3A-3D. In other examples of thepresent invention, the towers may be of various shapes, sizes, lengths,etc. for various patient anatomies. The assembly 800 and any of theexemplary assemblies and instruments for spondylolisthesis reduction maybe used with various styles of towers as the coupling features such asquick release mechanisms 212 and 412 may be modified for other styles ofconnections.

Example embodiments of the methods and systems of the present inventionhave been described herein. As noted elsewhere, these exampleembodiments have been described for illustrative purposes only, and arenot limiting. Other embodiments are possible and are covered by theinvention. Such embodiments will be apparent to persons skilled in therelevant art(s) based on the teachings contained herein. Thus, thebreadth and scope of the present invention should not be limited by anyof the above-described exemplary embodiments, but should be defined onlyin accordance with the following claims and their equivalents.

The invention claimed is:
 1. A system for reducing deformities in aspine, comprising: a first tower assembly; a first reduction assemblyoperably coupled to a proximal end of the first tower assembly; a secondtower assembly; a second reduction assembly operably coupled to aproximal end of the second tower assembly, the second reduction assemblyfurther comprising a reduction drive assembly, wherein the reductiondrive assembly comprises a rack driven by a pinion gear; wherein thesecond reduction assembly is operably coupled to the first reductionassembly via the reduction drive assembly, such that the reduction driveassembly transmits a leverage to the first reduction assembly causing itto move proximally relative to the second reduction assembly.
 2. Thesystem of claim 1, wherein the first reduction assembly furthercomprises a load transfer link receiver and the second reductionassembly further comprises a load transfer link member.
 3. The system ofclaim 2, wherein the load transfer link member and the load transferlink receiver are operably engaged and freely translatable relative toone another.
 4. The system of claim 2, wherein the load transfer linkmember is disposed at an end of the rack.
 5. The system of claim 1,further comprising a locking lever operably coupled to the pinion gear.6. The system of claim 1, wherein the first reduction assembly and thesecond reduction assembly are operably coupled by a load transfer linkmember, at least a portion of the member having stepped features todefine a ratcheted portion, and a load transfer link receiver, at leasta portion of the receiver being configured to engage the ratchetedportion of the member.
 7. The system of claim 1, wherein the racktranslates in a single plane relative to the second reduction assembly.8. The system of claim 1, wherein the rack translates along a curvedpath having a center of rotation located at a position inferior to thesecond tower.
 9. The system of claim 1, wherein the reduction driveassembly further comprises a reduction lever operably coupled to thepinion gear and the second reduction assembly further comprises a handlemember.
 10. The system of claim 9, wherein the reduction drive assemblyfurther comprises a reduction pawl operably coupled to the reductionlever and the pinion gear and a locking pawl operably coupled to therack.
 11. A system for reducing deformities in a spine, comprising: afirst tower assembly configured to attach to a first vertebra and extendin a posterior direction relative to the first vertebra; a firstreduction assembly operably coupled to a proximal end of the first towerassembly; a second tower assembly configured to attach to a secondvertebra and extend in a posterior direction relative to the secondvertebra, the second vertebra being caudal to the first vertebra; asecond reduction assembly operably coupled to a proximal end of thesecond tower assembly, the second reduction assembly further comprisinga reduction drive assembly, wherein the reduction drive assemblycomprises a rack driven by a pinion gear; wherein the reduction driveassembly is operably coupled to the first reduction assembly via therack, such that the reduction drive assembly transmits a leverage to thefirst reduction assembly to cause the first vertebra to move, relativeto the second vertebra, from an unreduced state into a reduce state. 12.The system of claim 11, wherein the first reduction assembly furthercomprises a load transfer link receiver and the second reductionassembly further comprises a load transfer link member.
 13. The systemof claim 12, wherein the load transfer link member and the load transferlink receiver are operably engaged and freely translatable relative toone another.
 14. The system of claim 12, wherein the load transfer linkmember is disposed at an end of the rack.
 15. The system of claim 11,further comprising a locking lever operably coupled to the pinion gear.16. The system of claim 11, wherein the first reduction assembly and thesecond reduction assembly are operably coupled by a load transfer linkmember, at least a portion of the member having stepped features todefine a ratcheted portion, and a load transfer link receiver, at leasta portion of the receiver being configured to engage the ratchetedportion of the member.
 17. The system of claim 11, wherein the racktranslates in a single plane relative to the second reduction assembly.18. The system of claim 11, wherein the rack translates along a curvedpath having a center of rotation located at a position caudal to thesecond vertebra.
 19. The system of claim 11, wherein the reduction driveassembly further comprises a reduction lever operably coupled to thepinion gear and the second reduction assembly further comprises a handlemember.
 20. The system of claim 19, wherein the reduction drive assemblyfurther comprises a reduction pawl operably coupled to the reductionlever and the pinion gear and a locking pawl operably coupled to therack.